Our Environment — Class 10 Science MCQ with Answers (2026-27)

Updated 23 August 2026 · checked against the CBSE 2026-27 syllabus

14 objective questions on Our Environment (Class 10 Science — Biology), every one checked against the CBSE 2026-27 syllabus. Pick an option and the correct answer is shown straight away, with your marks running at the top. A new question opens each day until all 14 are unlocked.

Our Environment MCQ questions with answers

1. Organisms and their food sources — Frog: cricket, grasshopper. Cricket: grass. Snake: frog, shrew. Shrew: cricket, grasshopper. Grasshopper: grass. Eagle: snake, shrew.
   Identify the primary consumer(s) in‌‌ the ecosystem.
   1. Snake
   2. Shrew
   3. Frog and Shrew
   4. Cricket and Grasshopper

   Answer: d) Cricket and Grasshopper

   Primary consumers eat producers directly. Crickets and grasshoppers feed on grass, while frogs, shrews and snakes eat other animals and so sit higher up.

2. Organisms and their food sources — Frog: cricket, grasshopper. Cricket: grass. Snake: frog, shrew. Shrew: cricket, grasshopper. Grasshopper: grass. Eagle: snake, shrew.
   A snake eats a frog.​​ What percentage of energy of the frog is transferred to the snake?
   1. 1%
   2. 2%
   3. 10%
   4. 90%

   Answer: c) 10%

   Only about 10% of the energy at one trophic level passes to the next; the rest is lost as heat and in life processes. This is the ten per cent law.

3. Organisms and their food sources — Frog: cricket, grasshopper. Cricket: grass. Snake: frog, shrew. Shrew: cricket, grasshopper. Grasshopper: grass. Eagle: snake, shrew.
   Which organism has the largest biomass in​‌ the ecosystem?
   1. Grass
   2. Snake
   3. Eagle
   4. Grasshopper

   Answer: a) Grass

   Biomass falls at each successive trophic level because energy is lost at every transfer. The producer at the base — grass — therefore has the greatest biomass.

4. The ozone layer of‌​ the atmosphere shields the Earth’s surface from the ultraviolet radiations of the Sun. Which of these is likely to increase in humans with depletion of the ozone layer?
   1. AIDS
   2. COVID
   3. Jaundice
   4. Skin Cancer

   Answer: d) Skin Cancer

   Ozone absorbs harmful ultraviolet radiation. With a thinner ozone layer more UV reaches the surface, and UV damages skin cells, raising the risk of skin cancer.

5. The primary source‌ of​ energy in an ecosystem is
   1. starch stored in plants
   2. glycogen stored in animals
   3. heat energy from respiration
   4. solar energy

   Answer: d) solar energy

   Every food chain begins with producers capturing sunlight. Starch and glycogen are stored forms of that energy, and heat from respiration is energy leaving the system.

6. If 10,000 J of solar energy falls on green plants in a terrestrial‌ ecosystem,‌ how much of it will be converted into food energy?
   1. 10,000 J
   2. 100 J
   3. 1000 J
   4. It will depend on the type of terrestrial plant.

   Answer: b) 100 J

   Green plants convert only about 1% of the sunlight falling on them into food energy, so 1% of 10,000 J is 100 J.

7. If Ravi is consuming curd for​ lunch,​ which trophic level in a food chain should he be considered as occupying?
   1. First trophic level
   2. Second trophic level
   3. Third trophic level
   4. Fourth trophic level

   Answer: c) Third trophic level

   Curd comes from milk, which comes from a cow that eats plants. Plant → cow → Ravi puts him at the third trophic level.

8. Decomposers are not included in​ the‌ food chain. The correct reason is that decomposers
   1. act at every trophic level of the food chain
   2. do not break down organic compounds
   3. convert organic material to inorganic forms
   4. release enzymes outside their body to convert organic material to inorganic forms

   Answer: a) act at every trophic level of the food chain

   Decomposers break down dead matter from producers and from consumers at every level, so they cannot be placed at any single step of a linear food chain.

9. Matter and‌ energy​ are two fundamental inputs of an ecosystem. Which statement describes their movement?
   1. Energy is bidirectional and matter is repeatedly circulating.
   2. Energy is repeatedly circulating and matter is unidirectional.
   3. Energy is unidirectional and matter is repeatedly circulating.
   4. Energy is multidirectional and matter is bidirectional.

   Answer: c) Energy is unidirectional and matter is repeatedly circulating.

   Energy enters as sunlight and is lost as heat at each level, so it flows one way and never returns. Matter, by contrast, is recycled endlessly through biogeochemical cycles.

10. Which of the following limits the number‌ of‌ trophic levels in a food chain?
    1. Decrease in energy at higher trophic levels
    2. Less availability of food
    3. Polluted air
    4. Water

    Answer: a) Decrease in energy at higher trophic levels

    Only about 10% of energy passes to each next level, so after four or five levels too little remains to support another. Energy loss, not food supply, sets the limit.

11. Choose the waste management strategy that is matched‌ with​ the correct example.
    1. Refuse — choose products that use less packaging
    2. Reduce — give unwanted toys and books to hospitals or schools
    3. Reuse — not using single-use plastic
    4. Repurpose — making a flower pot from a used plastic bottle

    Answer: d) Repurpose — making a flower pot from a used plastic bottle

    Repurposing means using a discarded item for a new purpose, which a bottle turned into a flower pot does exactly. The other three pair the term with the wrong example.

12. Under the Solid Waste Management Rules 2016,‌ waste‌ is segregated into three categories. Which row is correct?
    1. Wet: cooked food, vegetable peels | Dry: used bulbs, fluorescent lamps | Hazardous: plastic carry bags, bottles, newspaper, cardboard
    2. Wet: coffee and tea powder, garden waste | Dry: plastic carry bags, bottles, newspaper, cardboard | Hazardous: expired medicines, razors, paint cans
    3. Wet: leftover food, vegetable peels | Dry: coffee and tea powder, garden waste | Hazardous: insect repellents, cleaning solutions
    4. Wet: uncooked food, tea leaves | Dry: old crockery, frying pans | Hazardous: coffee and tea powder, garden waste

    Answer: b) Wet: coffee and tea powder, garden waste | Dry: plastic carry bags, bottles, newspaper, cardboard | Hazardous: expired medicines, razors, paint cans

    Wet waste is biodegradable kitchen and garden matter, dry waste is recyclable paper, plastic and metal, and hazardous waste is anything toxic such as expired medicines or razors.

13. Statements on the importance of waste segregation: (i) less waste goes to landfill, (ii) better for public health and the environment, (iii) helps in reducing the waste, (iv) results in deterioration of a waste picker’s health.
    Select the appropriate statements giving​ the​ importance of waste segregation.
    1. Both (i) and (ii)
    2. Both (i) and (iii)
    3. Both (ii) and (iii)
    4. Both (i) and (iv)

    Answer: a) Both (i) and (ii)

    Segregation keeps recyclables and hazardous items out of landfill (i) and protects health and the environment (ii). It does not by itself reduce the amount of waste (iii), and (iv) states a harm, not an importance.

14. When recycling a‌ plastic​ water bottle, what should you do with the cap?
    1. The cap goes into a garbage can and the bottle goes in a recycling bin
    2. Screw the cap back on the bottle, then put the bottle and cap in a recycling bin
    3. Screw the cap back on the bottle, then put the bottle and cap in the garbage can
    4. Recycle the cap separately

    Answer: a) The cap goes into a garbage can and the bottle goes in a recycling bin

    Caps are usually a different plastic from the bottle and are too small to be sorted by recycling machinery, so the cap is discarded and only the bottle is recycled.